Polyphenol Conjugates as RGD-Binding Compounds and Methods of Use

ABSTRACT

Provided herein are compositions and methods for preventing and treating diseases and risk factors associated with metabolic syndrome by targeting the RGD-binding site of selected intra- and extracellular proteins. Exemplary compositions include RGD-polyphenol conjugates via an ester linkage; polyphenol polymer conjugated to RGD analogs or mimetics; and RGD polymer conjugates linked to polyphenol.

FIELD OF THE INVENTION

The invention described herein pertains to compounds and methods for the prevention or treatment of conditions associated with metabolic syndrome, and more particularly to the use of resveratrol-like compounds in the treatment of such conditions.

BACKGROUND

Metabolic syndrome (or Syndrome X) is characterized by a group of metabolic risk factors in one person that include, for example, central obesity (i.e., excessive fat tissue in and around the abdomen), atherogenic dyslipidemia (i.e., blood fat disorders—mainly high triglycerides and low HDL cholesterol—that foster plaque buildups in artery walls), raised blood pressure (e.g., 130/85 mmHg or higher), insulin resistance or glucose intolerance (the body can't properly use insulin or blood sugar), prothrombotic state (e.g., high fibrinogen or plasminogen activator inhibitor in the blood), and proinflammatory state (e.g., elevated high-sensitivity C-reactive protein in the blood).

The underlying causes of this syndrome are overweight/obesity, physical inactivity and genetic factors. People with the metabolic syndrome are at increased risk of coronary heart disease, other diseases related to plaque buildups in artery walls (e.g., stroke and peripheral vascular disease) and type 2 diabetes.

Metabolic syndrome has become increasingly common in the United States. It's estimated that about 47 million U.S. adults have it. The syndrome is closely associated with a generalized metabolic disorder called insulin resistance, in which the body cannot use insulin efficiently. This is why the metabolic syndrome is also called the insulin resistance syndrome. Some people are genetically predisposed to insulin resistance. Acquired factors, such as excess body fat and physical inactivity, can elicit insulin resistance and the metabolic syndrome in these people. Most people with insulin resistance have central obesity. The biologic mechanisms at the molecular level between insulin resistance and metabolic risk factors are not fully understood and appear to be complex.

Conventional treatment typically includes dietary changes to limit fat and calories, increased exercise, and changes in habits or patterns of eating. Medications commonly prescribed for weight loss include numerous metabolic stimulants, perhaps in combination with cholesterol lowering drugs and/or high blood pressure medications. However, such compounds may not be effective in all subjects, or may be of limited efficacy. Accordingly, new treatments for metabolic syndrome and its associated factors are needed.

Caloric restriction is known to extend lifespan in mammals. Caloric restriction also reduces the incidence of age-associated conditions such as obesity, insulin resistance, dyslipidemia, and cancer. Resveratrol, a polyphenol derived from red wine, is a “phytoestrogen” that mimics caloric restriction by activating Sir2 and extending lifespan in several species. Resveratrol is also known to have anti-inflammatory and anti-angiogenic effects, as well as preventive effects to atherosclerosis.

Resveratrol has been shown to reduce fat accumulation in C. elegans and in several insulin-sensitive mammalian cell lines. Inhibition of AMP-activated kinase gene expression is also known to prevent the effect of resveratrol on fat accumulation. Accordingly, the effect of resveratrol on fat accumulation depends on Sir2.1. Thus, resveratrol-like compounds will prove useful in the prevention and treatment of diseases and risk factors associated with metabolic syndrome.

Consequently, it would be desirable to provide resveratrol analogs, resveratrol-like compounds, and polymers thereof, as well as methods of using such compounds in preventing and treating diseases and risk factors associated with metabolic syndrome.

SUMMARY

In view of the foregoing, it is an object of the present invention to provide resveratrol-like compounds and methods for preventing and/or treating diseases and risk factors associated with metabolic syndrome.

It is a further object of the invention to screen for resveratrol-like compounds

It is yet a further object of the present invention to provide methods of preventing and/or treating such disorders by targeting one or more RGD sites in selected intracellular or extracellular proteins.

Accordingly, these and other objects are accomplished by providing compounds and methods for preventing and/or treating diseases and risk factors associated with metabolic syndrome. In one aspect, the invention includes a compound that binds an RGD sequence is provided for the treatment of conditions associated with metabolic syndrome. The compound can include, but is not limited to, a polyphenol such as resveratrol, fisetin, butein, piceatannol, or quercetin, conjugated to a polymer.

In certain embodiments, the polymer can include, for example, polyvinyl alcohol, polyacrylic acid, polylactic acid, and other polymers with different molecular weight ranging from 2,000-20,000 Dalton.

In another aspect, the invention includes a compound that binds an RGD sequence and inhibits insulin/integrin-signaling to fat cell differentiation and fat cell accumulation. The compound can include, but is not limited to, resveratrol conjugated to a polymer, encapsulated inside or immobilized on nanoparticles, or mimetics and analogs or polymers thereof.

In another aspect, the invention includes methods of treating conditions associated with metabolic syndrome by administering a therapeutically effective amount of a compound that inhibits insulin-integrin-signaling via one or more intracellular lipogenic proteins, or one or more extracellular proteins, containing the RGD sequence. In particular embodiments, the insulin/integrin-signaling intracellular protein can include, for example, sirtuins, PI3 kinase, or SREBP. In other embodiments, the insulin-integrin-signaling extracellular protein can include, for example, IGFBP-1, VEGF, or osteopontin.

The invention also provides methods for identifying target peptides possessing RGD-containing binding sites by providing an affinity column containing at least one resveratrol-like compound or anti-angiogenic compound, contacting the target peptide with the affinity column, and collecting the target peptides that bind to the resveratrol-like compound or anti-angiogenic compound.

In still another aspect, the invention provides methods for identifying genes that are regulated in opposing directions by insulin and an RGD-binding compound by selectively stimulating expression of an unknown gene product that encodes the RGD sequence, isolating the gene product from control cells, resveratrol-stimulated cells and insulin-stimulated cells, alone and in combination, and analyzing the pools of gene product to identify genes regulated in opposing directions by insulin and RGD-binding compounds. In particular embodiments, the gene products can include, for example, mRNA or protein. In further embodiments, the analyzing step can include performing a gene expression microarray or mass spectroscopy to identify RGD containing gene products.

The invention further provides methods of screening a test compound for modulating insulin sensitivity via an intracellular protein containing an RGD sequence, via an extracellular protein containing an RGD sequence, or by using the promoter of a gene product that encodes the RGD sequence. In screening a test compound for modulating insulin sensitivity via an intracellular protein containing an RGD sequence, the method includes providing a transformed cultured cell line overexpressing a recombinant expression construct containing at least one RGD protein, and another transformed cultured cell line overexpressing a mutant derivative bearing RGE, adding a test compound to each of the cell cultures, assaying the cell cultures to determine whether the test compound is imported into the cell lines, assaying the cell cultures to determine whether the desired phenotypic change has occurred in wild-type but not mutant cell lines, and binding the test compound to the wild-type protein, but not the mutant protein, in vitro, wherein binding of the test compound to the wild-type protein indicates that the protein modulates insulin activity.

In screening a test compound for modulating insulin sensitivity via an extracellular protein containing an RGD sequence, the method includes providing a cultured preadipocyte cell line, adding the protein containing an RGD sequence and a mutant protein containing an RGE sequence to the preadipocyte cell culture, assaying the transformed cells to determine whether the desired phenotypic change has occurred in wild-type but not mutant proteins, adding the test compound in the presence and absence of the RGD and RGE containing proteins, assaying the transformed cell line to determine whether the test compound prevents fat cell differentiation and/or fact accumulation, and determining whether the test compound binds to the wild-type but not the mutant protein, wherein binding of the test compound to the wild-type but not the mutant protein indicates that the test compound modulates insulin sensitivity by reducing adipogenesis.

In screening a test compound for modulating insulin sensitivity by using the promoter of a gene containing an RGD sequence, the method includes providing a cultured cell line with a reporter gene driven by the promoter of a gene product regulated at the transcription level by insulin or an RGD-binding compound, adding insulin to the cell culture, adding an RGD-binding compound to the cell culture, assaying the transformed cell to determine whether the effect of insulin on the promoter is inhibited by the RGD-binding compound, assaying libraries for a hit, and determining whether the test compound binds a wild-type but not a mutant protein, wherein binding indicates that the test compound modulates insulin sensitivity.

In still a further aspect, the invention provides methods for inhibiting the activity or expression of a protein containing an RGD sequence involved in the insulin-signaling pathway by administering an effective amount of an RGD-binding compound to a subject suffering from an insulin-signaling disorder and/or a disorder associated with metabolic syndrome. In certain embodiments, the insulin-signaling disorder includes, but is not limited to, obesity, insulin resistance, diabetes, and complication thereof such as hyperlipidemia, cardiovascular disease, neurological disease, and renal disease. In other embodiments, the protein containing the RGD sequence is currently expressed, and the RGD-binding compound inhibits the active protein as well as the syntheses of new proteins containing the RGD sequence. In further embodiments the RGD-binding compound inhibits the activities and/or processes that regulate fat cell differentiation and fat accumulation.

Other features and advantages of the invention will be apparent from the detailed description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Representative polyphenols.

FIG. 2 Representative RGD analogs.

FIG. 3 Additional examples of RGD analogs.

FIG. 4 Polymer conjugates of polyphenolic compounds.

FIG. 5 Synthesis of polyphenolic polymer conjugates.

FIG. 6 Additional examples of polymer conjugates

FIG. 7 Polymer or protein bound catechin/epicatechin.

DETAILED DESCRIPTION

The details of one or more embodiments of the invention have been set forth in the accompanying description below. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. Other features, objects, and advantages of the invention will be apparent from the description and from the claims. In the specification and the appended claims, the singular forms include plural references unless the context clearly dictates otherwise. All patents and publications cited in this specification are incorporated by reference in their entirety.

For convenience, certain terms used in the specification, examples and claims are collected here. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

The term “agent” is used herein to denote a chemical compound, a mixture of chemical compounds, a biological macromolecule (such as a nucleic acid, an antibody, a protein or portion thereof, e.g., a peptide), or an extract made from biological materials such as bacteria, plants, fungi, or animal (particularly mammalian) cells or tissues. The activity of such agents may render it suitable as a “therapeutic agent” which is a biologically, physiologically, or pharmacologically active substance (or substances) that acts locally or systemically in a subject.

The term “RGD” as used herein refers to the single letter amino acid code and references the tripeptide amino acid sequence arginine-glycine-aspartic acid (Arg-Gly-Asp).

The term “RGD-binding compound” is used herein to mean a compound that modulates at least one activity of a protein encoding the amino acid sequence Arg-Gly-Asp.

The terms “peptide mimetic”, “mimetic”, or “peptidomimetic” as used herein refer to a compound that mimics at least one activity of a peptide or compound. For example, an RGD-binding compound mimetic refers to a compound that mimics a compound that modulates at least one activity of a protein encoding the amino acid sequence Arg-Gly-Asp.

A “form that is naturally occurring” when referring to a compound means a compound that is in a form, e.g., a composition, in which it can be found naturally. For example, since resveratrol can be found in red wine, it is present in red wine in a form that is naturally occurring. A compound is not in a form that is naturally occurring if, e.g., the compound has been purified and separated from at least some of the other molecules that are found with the compound in nature. A “naturally occurring compound” refers to a compound that can be found in nature, i.e., a compound that has not been designed by man. A naturally occurring compound may have been made by man or by nature.

“Sirtuin protein” refers to a member of the sirtuin deacetylase protein family or preferably to the Sir2 family, which include yeast Sir2 (GenBank Accession No. P53685), C. elegans Sir-2.1 (GenBank Accession No. NP_(—)501912), and human SIRT1 (GenBank Accession No. NM_(—)012238 and NP_(—)036370 (or AF083106), and SIRT2 (GenBank Accession No. NM_(—)030593 and AF083107) proteins. Other family members include the four additional yeast Sir2-like genes termed “HST genes” (homologues of Sir two) HST1, HST2, HST3 and HST4, and the five other human homologues hSIRT3, hSIRT4, hSIRT5, hSIRT6 and hSIRT7 (Brachmann et al. (1995) Genes Dev. 9:2888 and Frye et al. (1999) BBRC 260:273). Preferred sirtuins are those that share more similarities with SIRT1, i.e., hSIRT1, and/or Sir2 than with SIRT2, such as those members having at least part of the N-terminal sequence present in SIRT1 and absent in SIRT2 such as SIRT3 has.

“Diabetes” refers to high blood sugar or ketoacidosis, as well as chronic, general metabolic abnormalities arising from a prolonged high blood sugar status or a decrease in glucose tolerance. “Diabetes” encompasses both the type I and type II (Non Insulin Dependent Diabetes Mellitus or NIDDM) forms of the disease. The risk factors for diabetes include the following factors: waistline of more than 40 inches for men or 35 inches for women, blood pressure of 130/85 mmHg or higher, triglycerides above 150 mg/dl, fasting blood glucose greater than 100 mg/dl or high-density lipoprotein of less than 40 mg/dl in men or 50 mg/dl in women.

The term “hyperinsulinemia” refers to a state in an individual in which the level of insulin in the blood is higher than normal.

The term “insulin resistance” refers to a state in which a normal amount of insulin produces a subnormal biologic response relative to the biological response in a subject that does not have insulin resistance.

The term “metabolic syndrome” or “disorders or conditions associated with metabolic syndrome,” as discussed herein, refers to any disease or condition that is caused by or contributed to by insulin resistance. Examples include: diabetes, obesity, insulin-resistance syndromes, syndrome X, insulin resistance, high blood pressure, hypertension, high blood cholesterol, dyslipidemia, hyperlipidemia, dyslipidemia, atherosclerotic disease including stroke, coronary artery disease or myocardial infarction, hyperglycemia, hyperinsulinemia and/or hyperproinsulinemia, impaired glucose tolerance, delayed insulin release, diabetic complications, including coronary heart disease, angina pectoris, congestive heart failure, stroke, cognitive functions in dementia, retinopathy, peripheral neuropathy, nephropathy, glomerulonephritis, glomerulosclerosis, nephrotic syndrome, hypertensive enephrosclerosis, some types of cancer (such as endometrial, breast, prostate, and colon), complications of pregnancy, poor female reproductive health (such as menstrual irregularities, infertility, irregular ovulation, polycystic ovarian syndrome (PCOS)), lipodystrophy, cholesterol related disorders, such as gallstones, cholescystitis and cholelithiasis, gout, obstructive sleep apnea and respiratory problems, osteoarthritis, and prevention and treatment of bone loss, e.g. osteoporosis.

“Obese” individuals or individuals suffering from obesity are generally individuals having a body mass index (BMI) of at least 25 or greater. Obesity may or may not be associated with insulin resistance.

A “patient,” “individual,” “subject” or “host” refers to either a human or a non-human animal.

The term “modulation” is art-recognized and refers to up regulation (i.e., activation or stimulation), down regulation (i.e., inhibition or suppression) of a response, or the two in combination or apart.

The term “prophylactic” or “therapeutic” treatment is art-recognized and refers to administration of a drug to a host. If it is administered prior to clinical manifestation of the unwanted condition (e.g., disease or other unwanted state of the host animal) then the treatment is prophylactic, i.e., it protects the host against developing the unwanted condition, whereas if administered after manifestation of the unwanted condition, the treatment is therapeutic (i.e., it is intended to diminish, ameliorate or maintain the existing unwanted condition or side effects therefrom).

The term “mammal” is known in the art, and exemplary mammals include humans, primates, bovines, porcines, canines, felines, and rodents (e.g., mice and rats).

The term “pharmaceutically-acceptable salt” is art-recognized and refers to the relatively non-toxic, inorganic and organic acid addition salts of compounds, including, for example, those contained in compositions described herein.

The term “pharmaceutically acceptable carrier” is art-recognized and refers to a pharmaceutically-acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, excipient, solvent or encapsulating material, involved in carrying or transporting any subject composition or component thereof from one organ, or portion of the body, to another organ, or portion of the body. Each carrier must be “acceptable” in the sense of being compatible with the subject composition and its components and not injurious to the patient. Some examples of materials which may serve as pharmaceutically acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer's solution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxic compatible substances employed in pharmaceutical formulations.

The terms “systemic administration,” “administered systemically,” “peripheral administration” and “administered peripherally” are art-recognized and refer to the administration of a subject composition, therapeutic or other material other than directly into the central nervous system, such that it enters the patient's system and, thus, is subject to metabolism and other like processes.

The terms “parenteral administration” and “administered parenterally” are art-recognized and refer to modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intra-articulare, subcapsular, subarachnoid, intraspinal, and intrasternal injection and infusion.

“Treating” a condition or disease refers to curing as well as ameliorating at least one symptom of the condition or disease.

The term “therapeutic agent” is art-recognized and refers to any chemical moiety that is a biologically, physiologically, or pharmacologically active substance that acts locally or systemically in a subject. The term also means any substance intended for use in the diagnosis, cure, mitigation, treatment or prevention of disease or in the enhancement of desirable physical or mental development and/or conditions in an animal or human.

The term “therapeutic effect” is art-recognized and refers to a local or systemic effect in animals, particularly mammals, and more particularly humans caused by a pharmacologically active substance. The phrase “therapeutically-effective amount” means that amount of such a substance that produces some desired local or systemic effect at a reasonable benefit/risk ratio applicable to any treatment. The therapeutically effective amount of such substance will vary depending upon the subject and disease or condition being treated, the weight and age of the subject, the severity of the disease or condition, the manner of administration and the like, which can readily be determined by one of ordinary skill in the art. For example, certain compositions described herein may be administered in a sufficient amount to produce a desired effect at a reasonable benefit/risk ratio applicable to such treatment.

The term “synthetic” is art-recognized and refers to production by in vitro chemical or enzymatic synthesis.

Compositions

RGD is the single letter amino acid code for arginine-glycine-aspartate. This tripeptide motif can be found in proteins of the extracellular matrix. Integrins link the intracellular cytoskeleton of cells with the extracellular matrix by recognizing this RGD motif. Without attachment to the extracellular matrix, cells normally undergo apoptosis. Soluble RGD peptides induce apoptosis and might be used as drugs against angiogenesis, inflammation and cancer mestastasis since small soluble peptides containing the RGD motif inhibit cell attachment and consequently induce apoptosis.

Provided herein are RGD-binding compounds for treating a variety of conditions associated, directly or indirectly, with metabolic syndrome. Exemplary compounds include, but are not limited to, various polyphenols conjugated to a polymer. Polyphenols can include, for example, resveratrol, fisetin, butein, piceatannol, quercetin, and analogs thereof. In a preferred embodiment, the polyphenol is resveratrol or a resveratrol-like compound (i.e., a resveratrol analog).

Exemplary polymers that the polyphenols can be conjugated with include, but are not limited to polyvinyl alcohol, polyacrylic acid, or polylactic acid with different molecular weight ranging from 2,000-20,000 Dalton.

The RGD-binding compounds disclosed herein can also be used for preventing fat cell differentiation and/or fat accumulation. In addition to polymer conjugated resveratrol, or analogs thereof, RGD-binding compounds can include, for example, RGD, and analogs or polymers thereof. In one embodiment, a polymer conjugated RGD analog can include an integrin antagonist that inhibits angiogenesis.

Structure models for RGD-binding compounds contemplated by the present invention are more fully described in FIGS. 1-7.

The Role of Resveratrol or Resveratrol-Like Compounds, Analogs, and Polymeric Conjugations in Affecting Insulin-Sensitivity

Also provided herein are methods for treating a variety of conditions, directly or indirectly, associated with metabolic syndrome. In one embodiment, the method includes administering to a subject in need thereof a therapeutically effective amount of a compound that binds to one or more intra-cellular or extra-cellular lipogenic proteins encoding the amino acid sequence Arg-Gly-Asp (i.e., an RGD-binding compound). Such RGD-binding compounds inhibit insulin/integrin signaling, thereby treating conditions associated with metabolic syndrome.

Intra-cellular proteins contemplated by the present invention include, but are not limited to sirtuins, PI3 kinase, and sterol regulated binding protein-1 (“SREBP-1”). Extra-cellular proteins contemplated by the present invention include, but are not limited to, insulin-like binding protein-1 (“igfbp-1”), vascular endothelial growth factor (“vegf”), and osteopontin

As before, the compounds that bind the RGD sequence encoded by the intra-cellular or extra-cellular proteins include, for example, polymer conjugated resveratrol or analogs thereof, and RGD analogs and polymers thereof.

Screens for Identifying Peptides Encoding the Amino Acid Sequence Arg-Gly-Asp which Mediate the Adverse Effects of Conditions Associated with Metabolic Syndrome

Also provided are methods for identifying target peptides encoding the amino acid sequence Arg-Gly-Asp. Such peptides often mediate the adverse effects of conditions associated with metabolic syndrome via signaling pathways, e.g., the insulin-signaling pathway or the integrin-signaling pathway. In one embodiment, the method can include providing an affinity column containing at least one compound that binds to the amino acid sequence Arg-Gly-Asp, contacting the target peptides with the at least one compound in the affinity column, and collecting the target peptides that bind to the compounds in the affinity column. Target peptides that bind to the compounds in the affinity column contain a functional RGD binding site.

In another aspect, methods for identifying genes encoding the amino acid sequence Arg-Gly-Asp that are regulated in opposing directions by insulin and at least one RGD-binding compound are provided. One method features selectively stimulating expression of an unknown gene product that encodes the amino acid sequence Arg-Gly-Asp, isolating the gene product from control, resveratrol- and insulin-stimulated cells alone and in combination, pooling the gene products, and analyzing the pools of gene product to identify genes regulated in opposing directions by insulin and at least one RGD-binding compound. In a preferred embodiment of the method, the analyzing step includes performing a gene expression microarray. In another embodiment, the analyzing step includes performing mass spectroscopy. The gene product can be mRNA or a protein.

Also provided are methods of screening for indicators of insulin sensitivity that encode the amino acid sequence Arg-Gly-Asp. One method includes providing an affinity column containing at least one compound that binds to the amino acid sequence Arg-Gly-Asp, introducing serum collected from a subject exposed to nutritional manipulations, or from a subject afflicted with a condition associated with metabolic syndrome to the column, wherein the serum contains at least one indicator of insulin sensitivity, and collecting at least one indicator that binds to the compounds in the affinity column. An indicator that binds to the compounds in the affinity column encodes the amino acid sequence Arg-Gly-Asp and represents an indicator of insulin sensitivity. In a preferred embodiment, the indicators are extra-cellular secretory proteins.

Screens for Identifying Resveratrol-Like Compounds which Bind to Peptides Encoding the Amino Acid Sequence Arg-Gly-Asp.

In a further aspect, the invention also provides methods of screening a test compound for modulating insulin sensitivity. The target compound can modulate insulin activity by preventing insulin stimulated fat cell differentiation or insulin stimulated fat accumulation, or by potentiating insulin stimulated fat cell differentiation or insulin stimulated fat accumulation. One method includes providing a cell culture comprising a first cell line overexpressing a recombinant expression construct containing at least one intra-cellular protein encoding the amino acid sequence Arg-Gly-Asp, and a second cell line overexpressing a recombinant expression construct containing at least one mutant derivative of the protein expressed in said first cell line. The test compound can then be added to the Cell culture and the cell culture assayed to determine whether the test compound is taken up by the first and second cell lines. The first and second cell lines can also be assayed to determine whether the test compound binds the protein expressed by the first and second cell line. Binding of the test compound to the protein expressed by the first cell line, but not the protein expressed by the second cell line, indicates that the test compound modulates insulin activity.

In a preferred embodiment of the method, the mutant derivative encodes the amino acid sequence Arg-Gly-Glu, which is different at only one amino acid location from the wild-type protein. In another embodiment, the first cell line in step (a) can alternatively contains an extra-cellular protein encoding the amino acid sequence Arg-Gly-Asp. The first and second cell line can contain, for example, preadipocytes.

In a further embodiment, the first cell line in step (a) can alternatively contain a reporter gene driven by the promoter of a gene product encoding the amino acid sequence Arg-Gly-Asp, whereas the second cell line in step (a) can alternatively contain a reporter gene driven by the promoter of a gene product encoding the amino acid sequence Arg-Gly-Glu (i.e., a mutant to the gene product expressed by the first cell line). This embodiment can further feature the step of adding insulin to the cell culture prior to adding the test compound to the cell culture. In a further embodiment, the assaying step can include determining whether the test compound binds the promoter expressed by the first and second cell line. Binding of the test compound to the promoter expressed by the first cell line, but not the promoter expressed by the second cell line, indicates that the test compound modulates insulin activity. Using this method, libraries of compounds can be screened to determine if the library contains compounds capable of binding to the amino acid sequence Arg-Gly-Asp, which is an indicator of a potential pharmaceutical that binds to proteins encoding the Arg-Gly-Asp amino acid sequence that mediates various signaling pathways in conditions associated with metabolic syndrome.

Methods for Inhibiting Peptides Encoding the Amino Acid Sequence Arg-Gly-Asp which Affect Insulin Sensitivity

The present invention also provides methods for inhibiting the activity or expression of a protein encoding the amino acid sequence Arg-Gly-Asp. The method can include administering to a subject in need thereof an effective amount of an RGD-binding compound. In a preferred embodiment, the RGD-binding compound is polymer conjugated resveratrol, or analogs thereof.

A typical subject in need of administration of an RGD-binding compound as contemplated herein can include those suffering from a variety of conditions associated with metabolic syndrome. For example, the subject may be afflicted with any one, or a combination, of the conditions selected from the group consisting of insulin resistance, diabetes, obesity, insulin-resistance syndromes, syndrome X, high blood pressure, hypertension, high blood cholesterol, dyslipidemia, hyperlipidemia, atherosclerotic disease including stroke, coronary artery disease or myocardial infarction, hyperglycemia, hyperinsulinemia and/or hyperproinsulinemia, impaired glucose tolerance, delayed insulin release, diabetic complications, including coronary heart disease, angina pectoris, congestive heart failure, stroke, cognitive functions in dementia, retinopathy, peripheral neuropathy, nephropathy, glomerulonephritis, glomerulosclerosis, nephrotic syndrome, hypertensive enephrosclerosis, some types of cancer (such as endometrial, breast, prostate, and colon), complications of pregnancy, poor female reproductive health (such as menstrual irregularities, infertility, irregular ovulation, polycystic ovarian syndrome (PCOS)), lipodystrophy, cholesterol related disorders, such as gallstones, cholescystitis and cholelithiasis, gout, obstructive sleep apnea and respiratory problems, osteoarthritis, and prevention and treatment of bone loss, e.g. osteoporosis.

In one embodiment, the method is useful for inhibiting synthesis of new proteins encoding the amino acid sequence Arg-Gly-Asp, and/or inhibiting proteins that are currently expressed. Such proteins can be involved in the insulin-signaling and/or integrin-signaling pathways.

In another embodiment of the method, the RGD-binding compound regulates fat cell differentiation and/or fat accumulation by inhibiting a regulatory component involved in the activity or synthesis of the protein encoding the amino acid sequence Arg-Gly-Asp. The regulatory component can include, for example, any one, or a combination, of a member selected from the group consisting of: insulin regulation, the effect of nutritional manipulation or inflammatory processes, hormone/nuclear receptor regulation, and coregulatory proteins that alter activity or synthesis of transcription factors that regulate fat cell differentiation and fat accumulation.

Formulations

The RGD-binding compounds described above are preferably administered in a formulation including analogs or polymeric forms, and derivatives together with an acceptable carrier for the mode of administration. Any formulation or drug delivery system containing the active ingredients, which is suitable for the intended use, as are generally known to those of skill in the art, can be used. Suitable pharmaceutically acceptable carriers for oral, rectal, topical or parenteral (including subcutaneous, intraperitoneal, intramuscular and intravenous) administration are known to those of skill in the art. The carrier must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

Formulations suitable for parenteral administration conveniently include sterileaqueous preparation of the active compound, which is preferably isotonic with the blood of the recipient. Thus, such formulations may conveniently contain distilled water, 5% dextrose in distilled water or saline. Useful formulations also include concentrated solutions or solids containing the compound of formula (I), which upon dilution with an appropriate solvent give a solution suitable for parental administration above.

For enteral administration, a compound can be incorporated into an inert carrier in discrete units such as capsules, cachets, tablets or lozenges, each containing a predetermined amount of the active compound; as a powder or granules; or a suspension or solution in an aqueous liquid or non-aqueous liquid, e.g., a syrup, an elixir, an emulsion or a draught. Suitable carriers may be starches or sugars and include lubricants, flavorings, binders, and other materials of the same nature.

A tablet may be made by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active compound in a free-flowing form, e.g., a powder or granules, optionally mixed with accessory ingredients, e.g., binders, lubricants, inert diluents, surface active or dispersing agents. Molded tablets may be made by molding in a suitable machine, a mixture of the powdered active compound with any suitable carrier.

A syrup or suspension may be made by adding the active compound to a concentrated, aqueous solution of a sugar, e.g., sucrose, to which may also be added any accessory ingredients. Such accessory ingredients may include flavoring, an agent to retard crystallization of the sugar or an agent to increase the solubility of any other ingredient, e.g., as a polyhydric alcohol, for example, glycerol or sorbitol.

Formulations for rectal administration may be presented as a suppository with a conventional carrier, e.g., cocoa butter or Witepsol S55 (trademark of Dynamite Nobel Chemical, Germany), for a suppository base.

Alternatively, the compound may be administered in liposomes or microspheres (or microparticles). Methods for preparing liposomes and microspheres for administration to a patient are well known to those of skill in the art. U.S. Pat. No. 4,789,734, the contents of which are hereby incorporated by reference, describes methods for encapsulating biological materials in liposomes. Essentially, the material is dissolved in an aqueous solution, the appropriate phospholipids and lipids added, along with surfactants if required, and the material dialyzed or sonicated, as necessary. A review of known methods is provided by G. Gregoriadis, Chapter 14, “Liposomes,” Drug Carriers in Biology and Medicine, pp. 287-341 (Academic Press, 1979).

Microspheres formed of polymers or proteins are well known to those skilled in the art, and can be tailored for passage through the gastrointestinal tract directly into the blood stream. Alternatively, the compound can be incorporated and the microspheres, or composite of microspheres, implanted for slow release over a period of time ranging from days to months. See, for example, U.S. Pat. Nos. 4,906,474, 4,925,673 and 3,625,214, and Jein, TIPS 19:155-157 (1998), the contents of which are hereby incorporated by reference.

In one embodiment, the RGD-binding compounds or its polymeric forms can be formulated into nanoparticles.

Preferred nanoparticles are those prepared from biodegradable polymers, such as polyethylene glycols, polyglycolide, polylactide and copolymers thereof. Those of skill in the art can readily determine an appropriate carrier system depending on various factors, including the desired rate of drug release and the desired dosage.

In one embodiment, the formulations are administered via catheter directly to the inside of blood vessels. The administration can occur, for example, through holes in the catheter. In those embodiments wherein the active compounds have a relatively long half life (on the order of 1 day to a week or more), the formulations can be included in biodegradable polymeric hydrogels, such as those disclosed in U.S. Pat. No. 5,410,016 to Hubbell et al. These polymeric hydrogels can be delivered to the inside of a tissue lumen and the active compounds released over time as the polymer degrades. If desirable, the polymeric hydrogels can have microparticles or liposomes which include the active compound dispersed therein, providing another mechanism for the controlled release of the active compounds.

The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing the active compound into association with a carrier, which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing the active compound into association with a liquid carrier or a finely divided solid carrier and then, if necessary, shaping the product into desired unit dosage form.

The formulations can optionally include additional components, such as various biologically active substances such as growth factors (including TGF-.beta., basic fibroblast growth factor (FGF2), epithelial growth factor (EGF), transforming growth factors .alpha. and .beta. (TGF alpha. and beta.), nerve growth factor (NGF), platelet-derived growth factor (PDGF), and vascular endothelial growth factor/vascular permeability factor (VEGF/VPF)), antiviral, antibacterial, anti-inflammatory, immuno-suppressant, analgesic, vascularizing agent, and cell adhesion molecule.

In addition to the aforementioned ingredients, the formulations may further include one or more optional accessory ingredient(s) utilized in the art of pharmaceutical formulations, e.g., diluents, buffers, flavoring agents, binders, surface active agents, thickeners, lubricants, suspending agents, preservatives (including antioxidants) and the like.

The invention will be further illustrated in the following non-limiting examples.

EXAMPLES Example 1 Size Measurement of Resveratrol Doped Poly(Lactic-Co-Glycolic Acid) (PLGA) or Poly(Lactic-Co-Glycolic Acid)/Polyvinyl Alcohol (PLGA/PVA) Nanoparticles by Dynamic Light Scattering (DLS)

Resveratrol nanoparticles were prepared. The size of the nanoparticles was determined by DLS (single emulsion/solvent evaporation method), and ranged from 100-300 nm. The surface of PLGA nanoparticles was coated with chitosan and/or PVA.

Example 2 Polymer Conjugated Polyphenols Activate AMPK and Stimulate Fat Mobilization

Polyphenols, such as resveratrol, have beneficial effects on dyslipidemia, which accelerates atherosclerosis in diabetes. Using HEPG2 cell models or 3T3 adipocyte models it the polymer conjugated polyphenols described herein were observed to activate AMPK and stimulate fat mobilization. Specifically, the polymer conjugated polyphenols described herein increased phosphorylation of AMPK and its downstream target, acetyl-CoA carboxylase (ACC), and they increased activity of AMPK. The polymer conjugated polyphenols described herein also prevented the lipid accumulation that occurred in HepG2 cells exposed to high glucose. These studies demonstrate that the polymer conjugated polyphenols described and claimed herein are useful as a new therapeutic avenue to treat hyperlipidemia and atherosclerosis specifically in diabetes via activating AMPK.

Other Embodiments

While the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims. 

1. A pharmaceutical composition for treating conditions associated with metabolic syndrome in a subject in need thereof, comprising a therapeutically effective dose of an RGD-binding compound, or mimetics thereof, comprising a polyphenol conjugated to a polymer.
 2. The pharmaceutical composition of claim 1, wherein said polyphenol is selected from the group consisting of resveratrol, fisetin, butein, piceatannol, quercetin, and mimetics and analogs thereof.
 3. The pharmaceutical composition of claim 2, wherein said polyphenol is resveratrol, or mimetics or analogs thereof.
 4. The pharmaceutical composition of claim 1, wherein said polymer is selected from the group consisting of polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polylactic acid, hyaluronic acid, polyamidoamine, and combinations thereof.
 5. A pharmaceutical composition for preventing fat cell differentiation or fat cell accumulation in a subject in need thereof, comprising a therapeutically effective dose of an RGD-binding compound, or mimetics thereof.
 6. The pharmaceutical composition of claim 5, wherein the compound is polymer conjugated resveratrol, or mimetics or analogs thereof.
 7. A method of treating conditions associated with metabolic syndrome comprising administering to a subject in need thereof a therapeutically effective amount of a pharmaceutical composition comprising a compound that binds to one or more intra-cellular lipogenic proteins encoding the amino acid sequence Arg-Gly-Asp.
 8. The method of claim 7, wherein said intra-cellular protein is selected from the group consisting of sirtuins, PI3 kinase, and sterol regulated binding protein-1.
 9. The method of claim 7, wherein said compound is polymer conjugated resveratrol or mimetics or analogs thereof.
 10. The method of claim 7, wherein the compound inhibits insulin/integrin signaling, thereby treating conditions associated with metabolic syndrome.
 11. A method of treating conditions associated with metabolic syndrome comprising administering to a subject in need thereof a therapeutically effective amount of a pharmaceutical composition comprising a compound that binds to one or more extra-cellular proteins encoding the amino acid sequence Arg-Gly-Asp.
 12. The method of claim 11, wherein said extra-cellular protein is selected from the group consisting of insulin-like binding protein-1 (igfbp-1), vegf, and osteopontin.
 13. The method of claim 11, wherein the compound inhibits insulin/integrin signaling, thereby treating conditions associated with metabolic syndrome.
 14. A method for identifying target peptides encoding the amino acid sequence Arg-Gly-Asp, the method comprising: (a) providing an affinity column containing at least one compound that binds to the amino acid sequence Arg-Gly-Asp; (b) contacting said target peptides with said at least one compound in said affinity column; and (c) collecting the target peptides that bind to the compounds in the affinity column, wherein the target peptides that bind to the compounds in the affinity column contain a functional RGD-binding site.
 15. A method for identifying genes encoding the amino acid sequence Arg-Gly-Asp that are regulated in opposing directions by insulin and at least one RGD-binding compound, the method comprising: (a) selectively stimulating expression of an unknown gene product that encodes the amino acid sequence Arg-Gly-Asp; (b) isolating said gene product from control, resveratrol- and insulin-stimulated cells alone and in combination; (c) pooling said gene products; and (c) analyzing the pools of gene product to identify genes regulated in opposing directions by insulin and at least one RGD-binding compound.
 16. The method of claim 15, wherein said analyzing step includes performing a gene expression microarray.
 17. A method of screening for indicators of insulin sensitivity that encode the amino acid sequence Arg-Gly-Asp, the method comprising: (a) providing an affinity column containing at least one compound that binds to the amino acid sequence Arg-Gly-Asp; (b) introducing serum collected from a subject exposed to nutritional manipulations, or from a subject afflicted with a condition associated with metabolic syndrome to said column, said serum containing at least one indicator of insulin sensitivity; and (c) collecting at least one indicator that binds to the compounds in the affinity column, wherein an indicator that binds to the compounds in the affinity column encode the amino acid sequence Arg-Gly-Asp and represents an indicator of insulin sensitivity.
 18. The method of claim 17, wherein said indicators are extra-cellular secretory proteins.
 19. A method of screening a test compound for modulating insulin sensitivity, the method comprising: (a) providing a cell culture comprising a first cell line overexpressing a recombinant expression construct containing at least one intra-cellular protein encoding the amino acid sequence Arg-Gly-Asp, and a second cell line overexpressing a recombinant expression construct containing at least one mutant derivative of the protein expressed in said first cell line; (b) adding the test compound to the cell culture; (c) assaying the cell culture to determine whether the test compound is taken up by the first and second cell lines; (d) assaying the first and second cell lines to determine whether the test compound binds the protein expressed by the first and second cell line, wherein binding of the test compound to the protein expressed by the first cell line, but not the protein expressed by the second cell line, indicates that the test compound modulates insulin activity.
 20. The method of claim 19, wherein said mutant derivative encodes the amino acid sequence Arg-Gly-Glu.
 21. The method of claim 19, wherein the first cell line in step (a) alternatively contains an extra-cellular protein encoding the amino acid sequence Arg-Gly-Asp.
 22. The method of claim 19, wherein the first and second cell line contains preadipocytes.
 23. The method of claim 19, wherein the test compound modulates insulin activity by preventing insulin stimulated fat cell differentiation or insulin stimulated fat accumulation.
 24. The method of claim 19, wherein the test compound modulates insulin activity by potentiating insulin stimulated fat cell differentiation or insulin stimulated fat accumulation.
 25. The method of claim 19, wherein the first cell line in step (a) alternatively comprises a reporter gene driven by the promoter of a gene product encoding the amino acid sequence Arg-Gly-Asp, and wherein the second cell line in step (a) alternatively comprises a reporter gene driven by the promoter of a gene product encoding the amino acid sequence Arg-Gly-Glu.
 26. The method of claim 19, further comprising the step of adding insulin to the cell culture prior to performing step (b).
 27. The method of claim 26, wherein the assaying step of step (d) includes determining whether the test compound binds the promoter expressed by the first and second cell line, wherein binding of the test compound to the promoter expressed by the first cell line, but not the promoter expressed by the second cell line, indicates that the test compound modulates insulin activity.
 28. The method of claim 19, wherein the method further comprises the step of assaying libraries for a hit.
 29. A method for inhibiting the activity or expression of a protein encoding the amino acid sequence Arg-Gly-Asp, the method comprising administering to a subject in need thereof a therapeutically effective amount of a pharmaceutical composition comprising an RGD-binding compound.
 30. The method of claim 29, wherein the RGD-binding compound is polymer conjugated resveratrol, or mimetics or analogs thereof.
 31. The method of claim 29, wherein the RGD-binding compound inhibits the synthesis of new proteins encoding the amino acid sequence Arg-Gly-Asp.
 32. The method of claim 29, wherein the protein is involved in the insulin-signaling pathway.
 33. The method of claim 29, wherein the RGD-binding compound regulates fat cell differentiation and/or fat accumulation by inhibiting a regulatory component involved in the activity or synthesis of the protein encoding the amino acid sequence Arg-Gly-Asp.
 34. The method of claim 33, wherein said regulatory component is any one, or a combination, of a member selected from the group consisting of: insulin regulation, the effect of nutritional manipulation or inflammatory processes, hormone/nuclear receptor regulation, and coregulatory proteins that alter activity or synthesis of transcription factors that regulate fat cell differentiation and fat accumulation. 